Method of producing water-absorbent solid cloth-like articles

ABSTRACT

A method of producing water-absorbent cloth-like articles is disclosed. A binderless cellulosic nonwoven fabric is placed in a mold and compressed under a pressure of 1100 to 1500 kg/cm 2 , preferably 1200 to 1300 kg/cm 2 . The molding so produced will recover to original form when water is added to it.

This invention relates to methods of producing compactly molded portablewater-absorbent cloth-like articles. More particularly the presentinvention relates to a method of producing compressed water-absorbentsolid cloth-like articles by compactly compressing and molding awater-absorbent cloth-like material which can be recovered to the shapeas before the compression by utilizing its water-absorbency when wateris added to it prior to its use.

The conventional cloth having a water-absorbency is required to bewater-absorbent, has therefore many pores and air gaps and isnecessarily so bulky as to have problems of a great defect in carryingit and of requiring a large amount of material in packing it. It hasbeen desired very much to solve these problems.

Also, a water-absorbent cloth-like article small in the bulk is verysuitable to picnics, travels and angling in respect of the portability.Therefore, a compact cloth-like article has been desired to be developedin this respect.

As one method of solving these problems, a method of molding towelscharacterized in that a towel folded in advance is painted with 5 to 30%by weight of an aqueous solution of a water-soluble paste agent so thatthe residual paste agent may be 0.1 to 5% on the weight of the towel, isthen put into any desired mold and is placed under a pressure of 5 to 60kg/cm² for more than 2 minutes is introduced in Japanese PatentLaid-Open No. 53690/1975.

In such method, a pipette, spraying nozzle or roller is used to applythe paste. The method is therefore very complicate. In order to preventthe molding from collapsing after being molded of the paste, thepressure must be retained for several minutes at the time of thecompression. Some paste to be used is likely to be detrimental orunpleasant. If the amount of the paste agent is small, the molding willbe insufficient. If it is too large, on the contrary, there will be aproblem in the use. The method involves many of such problems and cannot be said to be well satisfactory.

In order to improve these defects, there is suggested Japanese UtilityModel Laid-Open No. 36,565/1977 whose subject matter is a solidcake-like towel made by putting a towel or nonwoven fabric into anydesired mold and compressing and molding it under a compression pressureof 30 to 1,000 kg/cm². However, when the present inventors worked saidinvention by cutting a binderless cellulosic nonwoven fabric to be offixed dimensions and putting it into a desired mold, with the pressureless than 1,000 kg/cm², the fabric was recognized to be wrinkled in theperipheral wall part and to tend to swell on the peripheral edge of theupper surface part. This seems to be caused by the fact that thebinderless cellulosic nonwoven fabric is higher in the compressionelasticity than the towel or any other nonwoven fabric. Such form notonly impairs the commodity value in the appearance but is also likely toobstruct the continuous operation in case it is used in an automaticvendor.

As a result of making various studies on the operation to eliminate theabove described defects in molding a cellulosic nonwoven fabric of fixeddimensions into a water-absorbent solid cloth-like article, the presentinventors have completed the present invention by discovering that suchdefects as are described above are due to the shortage of the operatingpressure.

FIG. 1 is an elevation of a water-absorbent solid cloth-like article ofthe present invention.

FIG. 2 is an elevation of a solid cloth-like article of a control.

FIG. 3 is a vertically sectioned view of the solid cloth-like article ofthe control.

The present invention is to produce a compressed water-absorbent solidcloth-like article by putting a binderless cellulosic nonwoven fabricinto any desired mold and compressing and molding it under a pressure of1100 to 1500 kg/cm² or preferably 1200 to 1300 kg/cm² so that saidmolding may recover to the original form when water is added to it.

When the compression pressure at the time of the compression and moldingis less than 1100 kg/cm², the compressed molding will be wrinkled in theperipheral wall part and will swell on the peripheral edge of the uppersurface part, will not become flat and therefore will not be desirable.By the way, even if the compression pressure exceeds 1500 kg/cm², theform of the compressed product will be little different. However, if thewaste of the energy is considered, it will not be desirable. If thecompression pressure exceeds 2000 kg/cm², there will occur such problemthat the cloth to which water is added after the compression and moldingwill partly break or will remarkably reduce in the strength. It is notdesirable.

In case the water-absorbent cloth-like article compressed under theconditions of the present invention is used as wet, when water is addedto it, it will recover to be of the form as before the compression andwill be very convenient. In case the cloth-like article is used, forexample, as a wet rolled towel, when it is desired to be cold as insummer, cold water may be added to it and, when it is desired to be warmas in winter, warm water may be added to it. Thus it can be used at anydesired temperature. In case it is an object to absorb water as inblotting paper or a duster, the compressed article of the presentinvention very high in the water-absorbency will be functionallyoptimum. Further, as the compressed article is compact and is molded tobe of the same dimensions, it is convenient to handle in automaticvendors used well today and expected to more and more develop hereafter.Further, in the present invention, such impurity as a paste agent is notused and therefore the product is very sanitary, is not unpleasant inthe use and is advantageous in the quality. As in the above, it has verydesirable points in the form and quality.

By the way, a binderless cellulosic nonwoven fabric developed by thepresent applicant company (suggested, for example, in U.S. Pat. No.3,832,281, Italian Pat. No. 962,732, West German Pat. No. 2,232,966) isvery desirable as a material to be compressed according to the presentinvention, and the material may have a water content of lower than 50%.

The present invention shall be explained with examples in the following:

EXAMPLE 1

A binderless cellulosic nonwoven fabric ("TCF", Trade mark of binderlesscellulosic nonwoven fabrics produced by Mitsubishi Rayon Co.) was cut tobe of 30×30 cm (about 5 g) and was folded to be about 7 cm wide. Thethree sheets were rolled together to be cylindrical and were put into acylindrical metal mold of a diameter of about 30 mm. The fabric withinthe mold was compressed under a pressure of about 1200 kg/cm². When thenonwoven fabric was then taken out, such solid cloth-like article of adiameter of 30 mm and a height of 10 mm was obtained. When water wasadded to this article, a cylindrical wet rolled towel recovered to be ofa height of 6 cm was obtained. Until water was added after thecompression and molding, the compressed nonwoven fabric did not vary inthe form. Further, after water was added, the nonwoven fabric wasnothing different in the strength from before the compression.

CONTROL 1

A solid cloth-like article was obtained by exactly the same method as inExample 1 except that the pressure at the time of compression andmolding was 1000 kg/cm². This cloth-like article was somewhat short inthe pressure at the time of molding and therefore had such appearancesas in FIGS. 2 and 3 on the attached sheet.

CONTROL 2

A solid cloth-like article was obtained by exactly the same method as inExample 1 except that the pressure at the time of compression andmolding was 2000 kg/cm². This cloth-like article was stable in the formbut was low in the strength when recovered to the original form byadding water, was broken in some place and could not function as acompressed nonwoven cloth.

EXAMPLE 2

A cellulosic nonwoven fabric ("TCF") was cut to be of 30×30 cm (about 5g), was triply folded to be about 10 cm wide, was cylindrically rolledto be of a diameter of 20 mm and was put into a cylindrical metal mold.The fabric within the mold was compressed under a pressure of about 1500kg/cm². When the nonwoven fabric was then taken out, such solidcloth-like article of a diameter of 20 mm and a height of 15 mm as inFIG. 1 was obtained. When water was added to this cloth-like article, acylindrical wet rolled towel recovered to be of a height of about 8 cmwas obtained. Until water was added after the compression and molding,the compressed cellulosic nonwoven fabric did not vary in the form.After water was added, the nonwoven fabric was not different at all inthe strength from before the compression.

We claim:
 1. A method of producing a water-absorbent solid cloth-likearticle characterized by putting a binderless cellulosic nonwoven fabricinto any desired mold and compressing and molding said binderlesscellulosic nonwoven fabric under a pressure of 1100 to 1500 kg/cm² togive said fabric a water-absorption recovering property.
 2. A method inaccordance with claim 1, wherein said pressure is 1,200 to 1,300 kg/cm².